苹果中5种氨基甲酸酯类农药的超临界流体萃取及其气相色谱法测定

提出了一种采用超临界流体萃取技术对苹果中５种氨基甲酸酯类农药进行萃取及用气相色谱检测的方法。实验以二氧化碳作为超临界流体，加入３％的甲醇作为改性剂，对３种惰性载体和加入硅藻土的苹果基体的超临界萃取条件进行了选择，以气相色谱配以氮磷检测器检测５种氨基甲酸酯类农药，取得了满意的结果，回收率为８８％～９８％。     

苹果中5种氨基甲酸酯类农药的超临界流体萃取及其气相色谱法测定

 提出了一种采用超临界流体萃取技术对苹果中５种氨基甲酸酯类农药进行萃取及用气相色谱检测的方法。实验以二氧化碳作为超临界流体，加入３％的甲醇作为改性剂，对３种惰性载体和加入硅藻土的苹果基体的超临界萃取条件进行了选择，以气相色谱配以氮磷检测器检测５种氨基甲酸酯类农药，取得了满意的结果，回收率为８８％～９８％。     

MECC保留值与logP的相关性

研究了不同有机改性剂下胶束电动毛细管色谱 (MECC)中电中性化合物的保留值与其正辛醇 水分配系数 (logP)间的相关性。结果表明 :溶质在MECC中的保留值 (logk′)与logP的相关性决定于MECC体系在分配行为上与正辛醇 水体系的相似性 ,用logk′w 代替logk′并不能改善相关性 ;溶质的受质子碱性是影响相关性的最主要的溶质性质 ;使用有机改性剂可以调节溶质在MECC体系中的分配行为接近于正辛醇 水体系 ,THF是调节溶质受质子碱性的影响的最佳有机改性剂 ;要使MECC体系在溶质分配行为上全面接近于正辛醇 水体系 ,同时加入两种作用相互补充的有机改性剂可能是更好的方法     

流动相组成对有机硒手性化合物拆分的影响

 在自制的涂敷型纤维素 三 (3,5 二甲基苯基氨基甲酸酯 ) (CDMPC)手性固定相上拆分了一些结构相似的有机硒手性化合物 ,详细考察了三元流动相对手性拆分的影响 ,并探讨了溶质分子与手性固定相相互作用的模式。实验结果表明 :在二元流动相中加入极少量的质子性改性剂 (醇 )或非质子性改性剂 (乙腈 ) ,可使溶质的保留和手性拆分发生较大的变化。     

多壁碳纳米管键合硅胶固定相的保留机理研究

制备了3种不同键合量的多壁碳纳米管键合硅胶固定相。以芳香族化合物为目标分析物,甲醇-水为流动相,分别考察了其在不同流动相比例、流速、柱温条件下,酸性、中性、碱性化合物的色谱保留行为,并通过计算分离过程中焓变、熵变和吉布斯自由能等热力学参数,探讨了色谱柱的保留机理。结果表明,碳纳米管键合硅胶与未键合的硅胶固定相分离对氨基苯磺酸和尿嘧啶时,因碳纳米管的加入增强了其疏水作用,保留机理与反相色谱柱相似。而分离中性化合物时,因加入的碳纳米管引入π-π作用,增强了对化合物的保留,有效地提高了色谱柱的柱效。碳纳米管的加入使溶质分子在固定相上的保留增强,溶质分子从杂乱无序排列转为有序排列,且溶质分子在不同碳纳米管键合量的色谱柱上的保留并非由单一机理支配,而是由多种作用相互协同的结果,这使碳纳米管键合硅胶固定相在分离和固相萃取领域展现出良好的应用前景。     

表面活性剂从碱性氰化液中萃取金

溶剂萃取法从碱性氰化液中提取金的工艺相对于传统锌置换法和活性炭吸附法具有潜在的优势,因而备受青睐。本文综述了近几年来从碱性氰化液中溶剂萃取金的研究进展。文中对表面活性剂/改性剂萃取Au(Ⅰ)的机理、萃取及反萃取行为进行了总结,报道了表面活性剂种类、改性剂种类、稀释剂以及盐析剂等各种因素对萃取过程的影响。同时,在萃取机理方面,提出一种基于氢键的超分子萃合物模型,在反萃取方面,介绍了阴离子交换法、转化还原法及直接电解有机相3种方法。     

中性溶质在反相毛细管电色谱中的保留行为

分别在以甲醇、乙腈、异丙醇和四氢呋喃为有机改性剂的４种二元流动相体系中对中性溶质在反相毛细管电色谱中的保留行为进行了研究。不仅考察了有机改性剂的种类和浓度对电渗淌度的影响,而且建立了溶质容量因子与有机改性剂在流动相中体积分数间的定量关系,此外还对样品在反相毛细管电色谱和反相毛细管高效液相色谱中的保留行为进行了比较,发现中性溶质在这两种分离模式中的容量因子基本相同。     

胶束溶液体系对毛细管电动色谱酸性化合物分离的影响

以阴离子表面活性剂十二烷基硫酸钠（SDS）、非离子表面活性剂吐温20（ Tween 20）及两者组成的混合胶束体系作为毛细管胶束电动色谱（MECC）的分离介 质，进行4种结构相似的酸性化合物的MECC分离研究，考察了胶束的类型、表面活 性剂的浓度、缓冲溶液的pH值及有机改性剂乙醇对分离的影响。结果表明各因素对 酸性药物的MECC分离有不同的影响规律。SDS胶束体系对溶质的保留值最大， Tween 20体系的保留值最小，二者的分离选择性正好相反，混合胶束体系的分离行 为则介于两者之间；在SDS和Tween 20体系中，表面活性剂浓度增加，溶质的保留 时间均随之递增，混合胶束体系中，总浓度一定，随Tween 20配比的增加，溶质的 保留时间先减少后增加；缓冲溶液的pH值增大，使溶质的分离效果均能变差；有机 改性剂乙醇的加入对容量因子的影响主要与溶质的疏水性有关，并对分离作用机理 进行了探讨。在SDS和Tween 20 MECC体系下，分别进行了实样测定，取得了满意的 结果。     

β-环糊精薄层色谱的研究和应用

本文讨论了邻、间和对苯二酚以β-环糊精水溶液为移动相,聚酰胺为固表相的薄层色谱。研究了影响溶质保留值的此素。结果表明,保留值和层析温度,β-环糊精浓度及在移动相中加入的有机改性剂有关。     

用固相萃取技术富集水中多环芳烃

系统地研究了淋洗剂强度、用量和有机改性剂的加入对固相萃取水中多环芳烃回收率的影响。研究表明,二氯甲烷和苯的洗脱效果较好,回收率为８７％～１０２％;当淋洗剂的用量超过１．５ｍＬ时,对多环芳烃的回收率没有明显的影响;向自来水样中加入２０％有机改性剂可明显改善多环芳烃的回收效果,使回收率达到８９％～１０８％。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.